The adult respiratory distress syndrome (ARDS) is an acute deterioration of lung function in patients with severe underlying diseases such as sepsis. It is likely that neutrophil proteases and oxidants contribute to the severity of the lung disorder. Two peptides were identified which may be responsible for the secretion of enzymes from the neutrophils which enter the lungs. These peptides are the neutrophil activating factor (NAF) and the enzymereleasing peptide (ERP) . One of them, NAF, may also attract neutrophils into the lungs. These studies will determine if it is likely that these peptides play an important role in exacerbating the lung disorder in patients with ARDS. They will also determine why they occur, why they are active, and which agents facilitate their secretion and action. Ultimately, it is only by reducing their activity in these patients that their clinical importance will be known. Therefore, many of these studies will focus on developing means of counteracting their activity.